Page 133 - phytochemistry general program

There are several ways in which paper can be modified for chromatography. .1
.2
It can be treated with a hydrophobic substance, so that it will support a non- .3
aqueous stationary phase (reversed phase).

It can be impregnated with a substance which will complex with one or more of the
substances being separated.

It can be given ion-exchange properties by combination with a resin or by chemical
modification (e.g. acetylation).

Stationary phases .4
I- Polar stationary phases
a- Aqueous stationary phase

b- Polar organic solvents
II- Non-polar (hydrophobic) stationary phases

Stationary phases

I- Polar stationary phases

a- Aqueous stationary phase

Water may be held stationary on a carrier.

Usually the paper takes up water from the atmosphere when it is suspended in a
closed chamber, where the atmosphere is saturated with water vapor.

b- Polar organic solvents

A polar organic solvent can be used as the stationary phase. This can be
volatile. e.g. methanol.

While with non-volatile polar organic solvents (e.g. formamide) the paper is drawn
through a solution of this solvent in a volatile organic solvent (e.g. methanol,

ethanol, acetone), then allowed to air-dry.

II- Non-polar (hydrophobic) stationary phases

With non-volatile stationary phases e.g. (paraffin oil, silicone oil), the paper is
impregnated in a solution of the stationary phase in a volatile non-polar organic

solvent e.g. petroleum ether, then air-dried.

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